Hi Hillhead,
The people who sold them to you have been irresponsible to claim that castrating would stop the horns growing! I wouldn't suggest disbudding them now, they are too old to go through the experience. However, as others have said, you can wire off the ends which are curling round and rubbing on their faces. I would say you do need to do this ASAP, as it must be causing discomfort.
Beth